The present invention relates to motion correction in diagnostic ultrasound. In particular, the present invention relates to methods and apparatus for acquiring and processing ultrasound data to reduce motion artifacts of ultrasound images.
At least some known ultrasound systems are capable of spatially compounding a plurality of ultrasound images of a given target into a compound image. The term “compounding” as used throughout means combining multiple data sets, each of which defines an image frame, non-coherently to create a new, single data set. The data sets may be obtained at different locations and/or may each be obtained at different times. The data sets or frames are combined to generate a single compound image by combining the corresponding data from each point in the compound image target. Real time spatial compound imaging may be performed by acquiring a series of partially overlapping component image frames from substantially independent locations. The component frames are combined into a compound image by estimating the location change, correcting for the estimated change and subsequently combining by summation, averaging, peak detection, or other combinational means. The compounded image may display a wider field of view.
In real time spatial compound imaging, several image frames are needed to produce each new compound image frame. A time difference exists between acquisition of the first frame used in constructing the compound image and the last frame used in the compound image. Significant image misregistration may exist due to the time difference between the acquisition of frames. The image misregistration may result in compound image blurring if a large number of image frames are used to construct the compound image. Relatively less blurring may result if a smaller number of image frames are used to construct the image. While it is generally desirable to acquire a large number of image frames, the large number of image frames requires a longer period of time for acquisition, during which blurring may increase to an undesirable level.
There are certain types of motion of the image target that are of interest, for example, the motion of a beating heart. However, undesirable motion also exists. Examples of causes for undesirable motion are the breathing of the patient being scanned, the movement of a fetus in a patient thus causing undesired movement of the image target, and undesirable movement of the ultrasound scanner by the operator. A need exists for improved methods and systems for motion correction in volumetric data sets.